6.1. Building the device-mapper module

Device mapper is in 2.6.9 and later, so you just need to make
sure it is enabled either as a module or builtin to the
kernel. Look for /sys/class/misc/device-mapper or look in
/proc/devices for a device-mapper entry to see if it is
enabled. If neither are there, try modprobe dm_mod, then
check again. For versions previous to 2.6.9, either you or
your distro must patch the kernel to support it. Check the
device
mapper web page for more information.